1. Field of the Invention
The present invention relates to a cleaning system for outer surfaces of tubes, which is available in pretreatment prior to non-destructive examination for performing thickness measurement or metallurgical structure inspection of a horizontal type tube assembly such as heat transfer tubes in a boiler.
2. Description of the Prior Art
Upon aging inspection for pipings of various plants such as boiler tubes and the like, in the preliminary stage for measurement of an outer diameter and a wall thickness which serve as a measure of a degree of wear and for discovery of flaws such as minute cracks, cleaning of the surfaces of the boiler tubes including, for instance, removal of firmly deposited ash or the like is performed, and thereafter in the inspection stage, a non-destructive examination such as, for example, liquid penetrant examination or the like is carried out.
As shown in FIG. 8, for instance, in the case where size examination for an outer diameter and a wall thickness of boiler heat transfer tubes formed in a panel shape and metallurgical structure inspection of the tubes are executed, since the interval between the adjacent tube panels is narrow, it has been often practiced that a worker would expand the panel interval by means of a jack, a chain block or the like (not shown) up to such extent that the works of cleaning, size examination and the like become possible in the space between the panels. Thereafter, generally the worker removes the ash firmly deposited on the outer surfaces of the boiler tubes by means of a commercially available JET-TAGANE (trade name) (jet-graver), a grinder or a hammer.
However, currently these works are carried out almost entirely by human labor, and execution of various kinds of examinations by labor-saving automation (remote-controlled operation) has been scarcely done in the prior art.
As described above, in the prior art since grinding and examination of an outer surface of a heat transfer tube was carried out by human labor, upon examination at a narrow place where a worker is not accessible, any one of the methods of expanding the interval between the panels by mechanical means as described above, cutting and taking out the panel to the outside of a boiler and then examining, and not performing examination but leaving the panel intact, was employed.
However, in the case of the former two methods, a lot of labor and expense were necessitated, and in the case of the last method, there remained the problem that a life and reliability of the various plants such as a boiler and the like would be degraded.
Especially in the recent years, it has been required to automate and systematize the cleaning step prior to examination, in which a cleaning device is accessible to a narrow interval without employing a scaffold and it removes solid ash and oxide scale deposited to the heat transfer tubes.